The present invention relates to solar thermal power systems, and more particularly, to geometric dome tower reflectors for solar thermal power systems.
High concentration solar thermal power systems rely on parabolic trough or dish concentrators or a field of heliostats to track the sun and reflect solar radiation onto receivers to heat a working fluid and drive a power conversion system to produce electricity, or to provide this thermal energy for various industrial and commercial processes. Similarly, tracking photovoltaic systems ensure that the solar irradiance incident on the solar arrays meet the appropriate optical requirements. For concentrating solar arrays, the tracking system can have essentially the same requirements as for troughs, dishes or heliostats, and in principle, the configurations can be very similar.
One type of solar power system utilizes what is known as xe2x80x9cbeam down optics.xe2x80x9d A beam down optics solar power system has a tower mounted reflector to reflect concentrated sunlight from hundreds or thousands of heliostats surrounding it to the ground where the light is concentrated and directed into a receiver. One such beam down optics solar power system is shown in U.S. Pat. No. 5,979,438.
The major design requirement that beam down optics solar power systems must meet is that the tower reflector and tower must be able to withstand the static and dynamic loads imposed primarily by wind and gravity (weight of the reflector, weight of the reflector with additional loads due to ice, and combinations of wind and gravity induced loads). Wind induced dynamic loads (wind gusts) impose particularly severe effects that could cause failure of the tower reflector.
It is an object of this invention to provide a low cost, easily assembled tower reflector that meets the above design requirement.
A geodome tower reflector for a beam down optics solar power system in accordance with this invention has a plurality of tower assemblies, preferably three. A geodome reflector assembly is movably mounted to the tower assemblies, preferably by mounting to guide shoes which move along a vertically extending guide rail of each tower assembly. The geodome reflector assembly has a facet support structure having a plurality of rigid frames to which facets are mounted. Each facet has a downwardly facing mirror for reflecting light from a heliostat to a receiver of the beam down optics solar power system.
In an embodiment, each tower assembly includes a hoist cable attached to its guide shoe. The hoist cables are coupled to a hoist mechanism for raising and lower the guide shoes to raise and lower the geodome reflector assembly.
A spreader assembly preferably spans tops of the tower assemblies and is secured to the tower assemblies. A plurality of guy wires are attached at one end to guy wire anchors and at other ends to individual tower assemblies. The spreader assembly and guy wires stabilize the tower assemblies.
In an embodiment, the geodome reflector assembly includes a frame surrounding the facet support structure with the facet support structure mounted to the frame in tension so that loads are transferred from the facet support structure to the frame. Clevis assemblies are preferably used to mount the facet support structure to the frame.
The facet support structure preferably includes a plurality of rigid triangular frames to which the facets are mounted. Each facet also has an aiming mirror that faces upwardly to a camera of a digital image radiometer that is mounted on the spreader assembly at the center thereof, preferably where radial trusses that preferably form part of the spreader assembly are joined together. The digital image radiometer and the aiming mirrors are used to adjust the facets. In this regard, the triangular frames of the facet support structure are adjustable in orientation with respect to each other.
The components of the tower reflector are fabricated to permit assembly on location utilizing relatively unsophisticated tools. The tower assemblies are preferably prefabricated in sections for assembly on location, such by being bolted or welded together, and the geodome reflector assembly is comprised of parts that can be assembled together on location to form the geodome reflector assembly, such by bolting together or by welding.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.